The invention relates to carriers for reticles used in photolithographic integrated circuit production, and more specifically to features for self-positioning of a reticle within a reticle carrier.
Integrated circuit devices are commonly manufactured using a process known as photolithography. In photolithography, a photoresist layer is first deposited on a wafer substrate. Radiant energy, such as ultraviolet light, is then projected onto the photoresist layer through a template in the form of a mask or reticle having the desired pattern. The photoresist layer is then developed to remove either the exposed portions or the unexposed portions, to form a resist mask on the substrate. The resist mask can then be used to protect underlying areas during later deposition or etching processes.
An important component of the photolithographic apparatus is the reticle, which provides the pattern and layout corresponding to the various integrated circuit features. Typically, the reticle is a transparent glass plate with a layer of opaque or semi-opaque material coated thereon forming the pattern. It is critically important that the surfaces of the reticle, especially the coated surface, be protected from damage or contamination, since any such defects or contamination may be projected onto the photoresist layer during exposure, thus leading to a finished integrated circuit device of unacceptably diminished or even unusable quality.
Specialized carriers have been developed to protect a reticle from physical damage and contamination during storage and transport. These carriers typically comprise an enclosure having various reticle contact portions therein for supporting and restraining the reticle from movement. The reticle is usually manually positioned on support surfaces within the enclosure, and the reticle is then engaged and more closely restrained against movement by restraint members attached within the enclosure. These restraint members are typically designed to engage the reticle at its edges. A problem, however, has been that a person initially manually positioning the reticle on the support surfaces may fail to place the reticle in the proper position for engagement by the restraint members, or may inadvertently cause the reticle to be dislodged from its proper positioning before it is engaged by the restraint members. If the reticle is out of position a sufficient distance, the restraint members may then engage the reticle on its surfaces rather than at its edges, thereby causing scratching or other physical damage to the reticle.
What is needed is some type of structure or device for ensuring proper self positioning of a reticle within a reticle carrier to prevent damage during engagement by restraint members.
The present invention provides a means of properly positioning a reticle in a carrier for engagement by reticle restraints while minimizing the opportunities for surface damage to the reticle inflicted by the reticle restraints. Also, with the present invention, manual positioning of the reticle on the reticle supports may be less precise, allowing for a greater margin for error.
The present invention is a reticle carrier having features for self-positioning of the reticle. In a currently most preferred embodiment of the invention, the carrier has a base portion and a cover portion. The base portion has reticle supports along with positioning tabs to guide proper manual positioning of the reticle on three sides. The base portion has no positioning tabs on the fourth side of the reticle. The cover portion has downwardly projecting self-positioning tabs having diagonal edges positioned so as to be engageable with the fourth side of the reticle. These downwardly projecting self-positioning tabs are oriented so that when the cover portion is placed over the base portion and pressed downward into engagement, the diagonal edges of the self-positioning tabs will engage an upper corner on the fourth side of the reticle, if the reticle is not properly positioned. As the cover portion is moved further downward into engagement with the base portion, the reticle is urged into proper position by the diagonal edges of the self-positioning tabs.
Accordingly, the present invention may be characterized in one embodiment as a carrier for a reticle used in photolithographic semiconductor processing, having a base portion and a cover portion. The base portion has a plurality of reticle supports and a plurality of reticle positioning members. The cover portion is adapted to sealingly mate with the base portion, and has an inner surface with a plurality of spaced apart reticle restraints and a pair of reticle positioning tabs projecting inwardly therefrom. Each reticle positioning tab has a diagonal edge portion, and is oriented so that the diagonal edge portion urges a reticle resting on the reticle supports into engagement with the reticle restraints when the cover portion is mated with the base portion.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.